I would check out the mapping resources forum here as people do post lots of collections of icons like that or scrape them off of old public domain maps which are then free to use. For things like dungeon chests and trapdoors and so on we have thousands of them as they are used on the virtual table tops. The regional maps are a little more scarce and the styles of them change a lot depending on the map but there are many to be viewed.

https://www.cartographersguild.com/f...splay.php?f=49